Fuel cell is a new technology and is the fourth type of power generation technology following water power, thermal power and nuclear power generation technologies. It is based on Redox reaction of oxygen or other oxidants to convert chemical energy in fuel into electrical energy. The most common fuel is hydrogen, other fuels may be any hydrocarbons which can be decomposed to obtain hydrogen, such as natural gas and pure methane, etc. Since not being restricted by Carnot cycle, the efficiency of fuel cell is theoretically greater than 80%, but the actual efficiency of fuel cell may be from 50% to 60%.
Solid Oxide Fuel Cell (SOFC) is a fuel cell technique using solid-state ceramic material as electrolyte. The operating temperature of the whole system is between 800° C. and 1000° C., which is categorized as high temperature fuel cell. Therefore, there are many material options to select, the materials can be selected include methane, natural gas, city gas, biomass, diesel and other hydrocarbons. When the hydrocarbon fuel is fed to the system, the feeding material is reformed first to generate the reformed gas mixture of hydrogen, carbon monoxide, carbon dioxide and steam, the electrochemical reaction occurs between the hydrogen and the oxygen at the cathode to generate electricity. Therefore, the advantages of high efficiency, being applicable to variety of fuels, and no requiring the use of precious metals as catalyst can be achieved. Simultaneously, the high temperature when operating may also be applied to increase power generation efficiency or to heat source supply, and thus it has high value of waste heat.
However, because the operating temperature of the solid oxide fuel cell system is extremely high, electronic gas heater is required to supply for the high temperature environmental condition, but the heater is a high energy-consuming device. Therefore, it may reduce the efficiency of the system if the heat source for fuel cell when operating will is provided by this manner. Next, due to the complexity of the solid oxide fuel cell system, there are many pipes connecting between components, which easily leads to heat loss along the pipeline and reduce efficiency of system. Furthermore, the high temperature waste heat generated when the system is operating cannot be reused effectively, so that energy consumption is increased vainly and it is harmful to the environment.